Most common types of environmental monitoring and control for irrigation systems incorporate a means of controlling the start time and duration of watering cycles via a central timing controller. The need to adjust a watering cycle due to the environmental influence is necessary in order to save natural resources, reduce costs, and to improve the growing environment for plants. Such environmental conditions include temperature changes, relative humidity, precipitation, wind and cloud cover.
In conventional control system, the primary means for halting an automatic watering cycle when certain environmental event occurs is by an operator manually suspending the cycle at the irrigation controller. In most situations this proves to be an ineffective means of conserving resources due to the inconsistent and inefficient methods followed by the operator. In fact, quite often the operator ignores the need to suspend the watering cycle altogether, and in some cases neglects to resume the watering cycle when required, leading to both over-watered and under-watered landscaping.
It is because of this unreliable and inconvenient manual method that environmental sensors were developed that allow for an automatic interruption of the controller due to an environmental condition. One of the major drawbacks of the conventional environmental sensors is the extensive installation time and difficult methods required for a proper installation.
A soil moisture sensor is usually installed in the ground by boring of a precisely sized hole, placing the sensor at the appropriate depth to measure the soil properties in the root zone, placing a slurry of water and soil in the hole to assure that the sensor has good contact with the soil and try to restore the soil in the hole to its previous condition as much as possible so that the sensor provides readings that correctly reflect the state of the soil. If the soil is not restored properly, water and fertilizer can drain down along the hole to the sensor and corrupt the sensor readings.
It is common for soil to be stratified into regions of varying textures, composition and drainage properties. Digging a hole and refilling it with slurry disrupts these strata around the sensor and decreases the accuracy of the sensor readings.
As the soil cycles from wet to dry, the soil may shrink back from the sensor and loose contact. If this happens, the sensor can no longer read the soil status properly. Sometimes, rewetting the soil is not sufficient to restore the sensor contact and the sensor must be reinstalled.
The wires that run from the sensors up through the soil to the surface are then routed either to a central controller directly or to a central controller through a wireless transmission system. This method is burdensome in time, tools required and is prone to unsuccessful installation through poor seating of the sensor in the soil, poor representation of the target soil by the sensed soil that was disturbed by installation, and electrical noise in connecting wires. The central controller receives the signals from the remote sensors and determines whether or not to start the next irrigation cycle for a particular irrigation zone.